Make Tmux-gitbar styles/colors optional

[arl]

Copy paste from issue #28, created by @adrianluff:

(Additionally), the current TMGB behavior requires duplicate, manual configuration of colors and styles in TMGB. This makes it unfriendly for use with plugins like vim-tmuxline. Further TMGB enhancement is possible by making TMGB colors and styles optional. I tested this by simply commenting two lines in tmux-gitbar.sh:

#tmux set-window-option "status-$TMGB_STATUS_LOCATION-style" "$TMGB_STYLE" > /dev/null
#tmux set-window-option "status-$TMGB_STATUS_LOCATION-length" 180 > /dev/null

This is only a partial solution but it allows the TMGB information to be combined with the user's existing tmux colorscheme or theme more easily.

An ideal implementation of this issue would have a conf file setting to enable or disable both of these enhancements rather than my hack-y solutions. Here's an example of what these changes allow.

[arl]

@adrianluff
It would be indeed very nice if tmux-gitbar would for allow seemless integration with vim-tmuxline, as with any other plugins or tools, while remaining usable, as it is now, with no needed user configuration in order to work on a vanilla installation. I like very much your idea of having a setting in the generated conf file.

What you propose is:
the current settings would remain the default, whereas if TGMB_NOSTYLE (for example) is set and equals to 1 in tmux-gitbar.conf the git bar would be rendered with no styles at all.

I'm wondering if there isn't even a simpler solution:
Did you try to set the TMGB_STYLE variable to the empty string in your tmux-gitbar.conf? If that is not enough, I guess it's because vim-tmuxline really needs to have the style not touched.

[adrianluff]

Setting readonly TMGB_STYLE='' in the tmux-gitbar.conf seems to work nicely for this.